DMB-T/H or DTMB (GB 20600-2006) is a digital terrestrial television Standard that is mandatorily applied in the People's Republic of China (PRC), including Hong Kong (referred to as the “Standard”). This mandatory Standard covers both fixed and mobile terminals devices, and may eventually serve more than half of the television viewers in the PRC, especially those in suburban and rural areas. The Standard uses two alternative modulation schemes: TDS-OFDM (Time Domain Synchronous-Orthogonal Frequency Division Multiplexing) which is a multi-carrier modulation scheme; and QAM (Quadrature Amplitude Modulation) which is a single-carrier modulation scheme.
The Standard generally defines the framing structure, channel coding and modulation for a digital television terrestrial broadcasting system. The technology of the Standard includes such things as pseudo number sequence frame headers which can be used for fast synchronization and high efficiency channel estimation/equalization and forward error correction (low density parity checking and BCH code). The Standard can support payload data rates of 4.813 Mbps to 32.486 Mbps, SDTV, HDTV, mobile and stationary reception, multi frequency networks and single frequency networks.
The Standard, according to one of the co-developers, is capable of transmitting “acceptable” signal qualities for an HDTV receiver moving at 200 km/h speed. The Standard also has the support of mobile digital TV service on handhelds which is absent from typical digital TV implementations in Europe and America. In addition to these, the radius of the area with signal coverage using the Standard is 10 km longer than the European implementation. Despite the advantages, there are also short comings of the Standard. As the Standard supports both single-carrier and multi-carrier modulation schemes, as well as not defining the default video encoding Standards, the research and development costs and complexity of the chip integrated circuits for this Standard are more significant, leading to more expensive receiver products.
Typically, receivers that support reception of both single carrier and multi-carrier signals, require more hardware components than receivers that can implement only one of the two types of signals. However, two completely separate receiver circuits are not necessarily required to implement all of the operations for processing broadcast modes of television signals that include either single carrier or multiple carrier signals. For example, since each of the two broadcast modes for either the single carrier or multiple carrier signals require substantially similar demodulation, forward error correction and symbol de-interleaving processes, some of the hardware and software components for processing the single carrier or multiple carrier signals could potentially be shared between two receivers. However, in the past, other operations for completing the processing for the two modes of broadcast television signals have employed separate equalizer circuits which are typically the largest sections/components of a receiver.
Differently arranged equalizers are typically provided to separately process single carrier or multiple carrier signals for broadcast television signals. For example, a receiver for processing multiple carrier signals usually includes a frequency domain equalizer that is based on a specialized mixed radix 3780 FFT (Fast Fourier Transform) engine for a FFT length of 3780 in combination with a complex division unit. However, such receivers arranged for processing multiple carrier signals often suffer from performance limitations in rejecting high bandwidth phase noise, which can be expensive to minimize. Alternatively, a receiver separately arranged to process single carrier signals for broadcast television signals usually includes a time domain equalizer that is based on relatively long and complex digital filters arranged in both feed-forward and feed-back formations.
Also, at least one drawback to a receiver that includes the 3780 FFT engine is its complexity and relatively high cost in comparison to other components included with the receiver. Thus, it would be advantageous to have a receiver arranged as an integrated circuit that is capable of processing both the single carrier and multiple carrier signals for broadcast television signals, and in which a substantial amount of such processing takes place with common components that do not make use of a 3780 FFT engine.